Unified media access control (mac) for multiple physical layer devices

ABSTRACT

A device implementing unified media access control (MAC) for multiple physical layer devices may include a MAC module communicatively coupled to first and second physical layer modules that are configured to communicate with another device over first and second physical wireless channels, respectively. The MAC module may be configured to receive one or more data items to be transmitted to the another device and to select at least one of the first or second physical layer modules for transmission of the one or more data items based at least in part on a first wireless link quality of the first physical wireless channel and a second wireless link quality of the second physical wireless channel. The MAC module may be further configured to provide the one or more data items to the selected at least one of the first or second physical layer modules for transmission to the another device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/470,163, entitled “Unified Multi-Layer MediaAccess Control (MAC) for Multiple Physical Layer Devices,” filed on Mar.10, 2017, which is hereby incorporated by reference in its entirety forall purposes.

TECHNICAL FIELD

The present description relates generally to media access control formultiple physical layer devices, including unified media access control(MAC) for multiple physical layer devices (PHYs).

BACKGROUND

Wireless devices may utilize one or more different wireless technologiesto communicate over one or more frequency bands, such as 2.4 gigahertz(GHz), 5 GHz 60 GHz, etc. The different wireless technologies may beassociated with different channel specific functions, such as channelaccess, link maintenance, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain features of the subject technology are set forth in the appendedclaims. However, for purpose of explanation, several embodiments of thesubject technology are set forth in the following figures.

FIG. 1 illustrates an example network environment in which a unified MACfor multiple PHYs may be implemented in accordance with one or moreimplementations.

FIG. 2 illustrates an example electronic device implementing a unifiedMAC for multiple PHYs in accordance with one or more implementations.

FIG. 3 illustrates an example electronic device implementing a unifiedMAC for multiple PHYs in accordance with one or more implementations.

FIG. 4 illustrates an example electronic device implementing a unifiedMAC for multiple PHYs in accordance with one or more implementations.

FIG. 5 illustrates a flow diagram of an example process of a primary MACmodule in a unified MAC for multiple PHYs in accordance with one or moreimplementations.

FIG. 6 illustrates a flow diagram of an example process of a secondaryMAC module in a unified MAC for multiple PHYs in accordance with one ormore implementations.

FIG. 7 conceptually illustrates an electronic system with which one ormore implementations of the subject technology may be implemented.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious configurations of the subject technology and is not intended torepresent the only configurations in which the subject technology may bepracticed. The appended drawings are incorporated herein and constitutea part of the detailed description. The detailed description includesspecific details for the purpose of providing a thorough understandingof the subject technology. However, the subject technology is notlimited to the specific details set forth herein and may be practicedusing one or more implementations. In one or more instances, structuresand components are shown in block diagram form in order to avoidobscuring the concepts of the subject technology.

In the subject system, a unified MAC module is provided for controllingmultiple different PHYs, such as for controlling concurrenttransmissions over multiple different PHYs. The PHYs may be configuredto communicate with a device over corresponding physical channels, suchas corresponding physical wireless channels, where each of the PHYs isconfigured to communicate with the device over a different one of thecorresponding physical channels. The unified MAC module receives datafor transmission to the device and selects one or more of the PHYs fortransmitting the data based at least in part on a quality of thedifferent physical wireless channels corresponding to the PHYs. Thequality may be, for example, a wireless link quality of the physicalwireless channels, or generally any indication of a quality of thephysical wireless channels. The unified MAC module provides the data tothe selected one or more PHYs for transmission to the device over thecorresponding physical wireless channels.

In one or more implementations, the unified MAC module may includemultiple MAC layers. For example, the unified MAC module may include aprimary MAC module that coordinates MAC functions that are common acrossthe different PHYs, such as packet assembly, retransmissions,acknowledgments, packet reordering, and the like, and secondary MACmodules that are each associated with a different one of the PHYs. Thesecondary MAC modules handle channel-specific (and/or PHY-specific) MACfunctions for the associated PHY, such as channel access (e.g., usingcarrier sense multiple access (CSMA)), link maintenance, and the like.In this manner each of the secondary MAC modules can be individuallyconfigured to handle the channel-specific (and/or PHY-specific) MACfunctions, e.g. functions whose implementations may differ across eachof the PHYs, while the primary MAC module can be configured to handlethe common MAC functions. Thus, the unified MAC module can be extended,e.g. by adding additional secondary MAC modules, to handle any number ofindividual PHYs and any type of individual PHYs. Furthermore, utilizingthe primary MAC module allows for the common MAC functions across allthe PHYs to be unified.

FIG. 1 illustrates an example network environment in which a unified MACfor multiple PHYs may be implemented in accordance with one or moreimplementations. Not all of the depicted components may be required,however, and one or more implementations may include additionalcomponents not shown in the figure. Variations in the arrangement andtype of the components may be made without departing from the spirit orscope of the claims as set forth herein. Additional components,different components, or fewer components may be provided.

The example network environment 100 includes one or more electronicdevices 102A-C. The electronic devices 102A-C may communicate with oneanother using one or more wireless communication technologies, such asWi-Fi (e.g. 802.11ac, 802.11ax, etc.), cellular (e.g. 3G, 4G, 5G, etc.),directional multi-gigabit (DMG), and/or mmWave (e.g. 802.11ad, 802.11ay,etc.). The electronic devices 102A-C may communicate with one anotherusing single carrier transmissions and/or multi-carrier transmissions,such as orthogonal frequency-division multiplexing transmissions.

The electronic devices 102A-C may be, for example, base stations, accesspoints, routers, portable computing devices such as laptop computers,smartphones, tablet devices, wearable devices such as a watch, a band,and the like, or any other appropriate device that includes, forexample, one or more wireless interfaces. In FIG. 1, by way of example,the electronic device 102A is depicted as a mobile device, theelectronic device 102B is depicted as a tablet device, and theelectronic device 102C is depicted as a base station. The electronicdevices 102A-C may be, and/or may include all or part of, the electronicdevices discussed below with respect to FIGS. 2-4, and/or the electronicsystem discussed below with respect to FIG. 7.

In one or more implementations, one or more of the electronic devices102A-B may communicate with the electronic device 102C, e.g. a basestation or access point, and/or the electronic devices 102A-B maycommunicate directly with one another using peer-to-peer transmissions,e.g. bypassing the electronic device 102C, and/or independent ofcoordination from the electronic device 102C. For explanatory purposes,multiple different wireless and wired technologies are described herein.However, the subject system is PHY-independent and can be uniformlyimplemented across generally any communication technology.

In the subject system, the electronic devices 102A-C may each include aunified MAC module for controlling multiple different PHYs. The unifiedMAC module allows for each of the electronic devices 102A-C tocommunicate over multiple different PHYs concurrently. The unified MACmodule supports any number/type of concurrent PHYs, such as realsimultaneous dual band (RSDB) communications with a 2.4 GHz PHY and a 5GHz PHY, single in-band communications with two 5 GHz PHYs, an 802.11ax2.4 GHz PHY and one or more 802.11ad PHYs, and the like.

The unified MAC module may support full duplex, frequency divisionduplexing (FDD), and/or multiple PHYs per band, such as multipledifferent 802.11ad PHYs. The unified MAC module supportstransmitting/receiving any packets (e.g. data, management, extension,acknowledgements, etc.) by any PHY or by one or more PHYs in any order.The data may be transmitted in chunks or in packets. The unified MACmodule further allows for the use of different PHYs for uplink/downlink,transmission/acknowledgment, transmission/retransmission, and the like.

The unified MAC module may select one or more PHYs to use for a giventransmission based on one or more parameters, such as link budget(assessed service availability) of the wireless channels correspondingto the PHYs, the amount of data to be transmitted, wireless link qualityof the channels corresponding to the PHYs (e.g., RSSI (Received SignalStrength Indication), SINR (Signal-to-Interference-plus-Noise Ratio),PDR (Packet-Delivery Ratio), and/or BER (Bit-Error Rate)), power impact,channel availability, delay, quality of service, and the like. Exampleunified MAC modules are discussed further below with respect to FIGS.2-4.

The unified MAC module may select different PHYs for transmissions todifferent devices, and/or different or the same data may be transmittedover multiple PHYs to the same device. For example, the unified MACmodule may select a first PHY for transmission of data from a first dataflow and the unified MAC module may select a second PHY for transmissionof data from a second data flow. In the instance where data is beingtransmitted to multiple different devices, the unified MAC module mayselect the most suitable PHY for each of the different devices, and/orthe unified MAC module may broadcast the data to each of the differentdevices over each of the multiple PHYs concurrently. In one or moreimplementations, the unified MAC module may select to transmit the samedata across multiple PHYs. In this instance, a unified MAC module of thereceiving device may combine the data received across the multiple PHYsand may drop the redundant packets, such as by using maximum ratiocombining.

In one or more implementations, the unified MAC module may include aprimary MAC module that coordinates functions that are common across thePHYs and individual secondary MAC modules associated with each PHY thathandle the channel-specific (or PHY-specific) functions for theassociated PHY. The primary MAC module may select which secondary MACmodule and associated PHY to use for a given transmission, e.g., basedon the aforementioned parameters. An example process of a primary MACmodule is discussed further below with respect to FIG. 5, and an exampleprocess of a secondary MAC module is discussed further below withrespect to FIG. 6.

FIG. 2 illustrates an example electronic device 102A implementing aunified MAC for multiple PHYs in accordance with one or moreimplementations. Not all of the depicted components may be used in allimplementations, however, and one or more implementations may includeadditional or different components than those shown in the figure.Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional components, different components, or fewer componentsmay be provided.

The electronic device 102A may include, among other components, aprocessor 202, a unified MAC module 204, one or more PHYs 210A-N, andone or more antennas 212A-N. The unified MAC module 204 may becommunicatively coupled to the processor 202, such as via one or moreinternet protocol (IP) interfaces. The one or more IP interfaces may beused to communicate one or more data flows between the processor 202 andthe unified MAC module 204. In this manner, the inner workings of theunified MAC module 204 and/or the PHYs 210A-N are transparent to theprocessor 202 and/or applications executing thereon.

The unified MAC module 204 may receive data from the processor 202,select one or more of the PHYs 210A-N for transmitting the data,packetize/process the data, and provide all or part of thepacketized/processed data to the selected PHYs 210A-N for transmissionover corresponding physical wireless channels. The unified MAC module204 may also receive data from the PHYs 210A-N,combine/depacketize/process the data, and provide the processed data tothe processor 202.

The processor 202, which may also be referred to as an application/hostprocessor, may include suitable logic, circuitry, and/or code thatenable processing data and/or controlling operations of the electronicdevice 102A. In this regard, the processor 202 may be enabled to providecontrol signals to various other components of the electronic device102A. The processor 202 may also control transfers of data to/from theelectronic device 102A. For example, the processor 202 may provide dataitems, such as packets, chunks, or a raw or unformatted data stream, tothe unified MAC module 204 for transmission by one or more of the PHYs210A-N, and the processor 202 may receive data items, such as packets,chunks, or a raw or unformatted data stream, from the unified MAC module204.

The PHYs 210A-N may be physical layer devices (or physical layermodules) for communicating over physical wireless channels on one ormore frequency bands, such as 2.4 GHz, 5 GHz, 60 GHz, or generally anyfrequency band. The PHYs 210A-N may each be separate circuits and/or thePHYs 210A-N may share one or more circuits or components. In one or moreimplementations, the PHYs 210A-N may share the one or more antennas212A-N. Each of the PHYs 210A-N may be configured for communication overa physical wireless channel on one of the frequency bands; however, thePHYs 210A-N may be reconfigurable for communication over others of thefrequency bands. In one or more implementations, one or more of the PHYs210A-N may be compliant with one or more specifications, such as802.11n, 802.11ax, 802.11ad, etc.

In one or more implementations, all or part of the unified MAC module204 may be implemented on dedicated circuitry and/or all or part of theunified MAC module 204 may be implemented by the processor 202. In oneor more implementations, the unified MAC module 204 may be backwardscompatible with one or more of 802.11n, 802.11ac, 802.11ax, etc., andthe unified MAC module 204 may provide extended functionality.

In one or more implementations, one or more of the processor 202, theunified MAC module 204, the PHYs 210A-N, and/or one or more portionsthereof, may be implemented in software (e.g., subroutines and code),hardware (e.g., an ASIC, an FPGA, a PLD, a controller, a state machine,gated logic, discrete hardware components, or any other suitabledevices) and/or a combination of both.

FIG. 3 illustrates an example electronic device 102A implementing aunified MAC for multiple PHYs in accordance with one or moreimplementations. Not all of the depicted components may be used in allimplementations, however, and one or more implementations may includeadditional or different components than those shown in the figure.Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional components, different components, or fewer componentsmay be provided.

The electronic device 102A may include, among other components, theprocessor 202, the unified MAC module 204, the one or more PHYs 210A-N,and the one or more antennas 212A-N. The unified MAC module 204 mayinclude a primary MAC module 306 and one or more secondary MAC modules308A-N. The primary MAC module 306 may be communicatively coupled to theprocessor 202, such as via one or more internet protocol (IP)interfaces. The primary MAC module 306 may also be communicativelycoupled to each of the secondary MAC modules 308A-N. In one or moreimplementations, there may be a single MAC address assigned to theunified MAC module 204. Accordingly, the single MAC address is sharedacross the primary MAC module 306 and the secondary MAC modules 308A-N.

The primary MAC module 306 may receive data from the processor 202,select one or more of the secondary MAC modules 308A-N and associatedPHYs 210A-N for transmitting the data, packetize/process the data, andprovide all or part of the packetized/processed data to the selectedsecondary MAC modules 308A-N for transmission. The primary MAC module306 may also receive data from the secondary MAC modules 308A-N,combine/depacketize/process the data, and provide the processed data tothe processor 202. An example process of the primary MAC module 306 isdiscussed further below with respect to FIG. 5.

The processor 202 may provide data items, such as packets, chunks, or araw or unformatted data stream, to the primary MAC module 306 fortransmission by one or more of the PHYs 210A-N, and the processor 202may receive data items, such as packets, chunks, or a raw or unformatteddata stream, from the primary MAC module 306.

The secondary MAC modules 308A-N may each be associated with, andcommunicatively coupled to, one of the PHYs 210A-N. The secondary MACmodules 308A-N may handle the channel/PHY specific functions withrespect to each of the PHYs 210A-N, such as channel access and/or linkmanagement with respect to respective channels over the PHYs 210A-N. Thesecondary MAC modules 308A-N may receive data from the primary MACmodule 306 and pass the data to the PHYs 210A-N for transmission overthe respective channels to one or more other electronic devices 102B-C,such as the electronic device 102C. Similarly, the secondary MAC modules308A-N may receive data from the PHYs 210A-N and may provide thereceived data to the primary MAC module 306. An example process of asecondary MAC module 308A is discussed further below with respect toFIG. 6.

In one or more implementations, all or part of the unified MAC module204 may be implemented on dedicated circuitry and/or all or part of theunified MAC module 204 may be implemented by the processor 202. Theprimary MAC module 306 may be implemented on a same integrated circuitas the secondary MAC modules 308A-N, or the primary MAC module 306 maybe implemented on a separate integrated circuit than one or more of thesecondary MAC modules 308A-N. The primary MAC module 306 and/or thesecondary MAC modules 308A-N may be configured to power on/off each ofthe corresponding PHYs 210A-N. In one or more implementations, theunified MAC module 204 may be backwards compatible with one or more of802.11n, 802.11ac, 802.11ax, etc., and the unified MAC module 204 mayprovide extended functionality.

In one or more implementations, one or more of the processor 202, theunified MAC module 204, the primary MAC module 306, the secondary MACmodules 308A-N, the PHYs 210A-N, and/or one or more portions thereof,may be implemented in software (e.g., subroutines and code), hardware(e.g., an ASIC, an FPGA, a PLD, a controller, a state machine, gatedlogic, discrete hardware components, or any other suitable devices)and/or a combination of both.

FIG. 4 illustrates an example electronic device 102A implementing aunified MAC for multiple PHYs in accordance with one or moreimplementations. Not all of the depicted components may be used in allimplementations, however, and one or more implementations may includeadditional or different components than those shown in the figure.Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional components, different components, or fewer componentsmay be provided.

The electronic device 102A may include, among other components, aprocessor 202, a unified MAC module 204, one or more PHYs 210A-N, andone or more antennas 212A-N. The unified MAC module 204 may include ahybrid primary/secondary MAC module 402 and one or more secondary MACmodules 308B-N. The hybrid primary/secondary MAC module 402 may becommunicatively coupled to the processor 202, such as via one or moreinternet protocol (IP) interfaces. The hybrid primary/secondary MACmodule 402 may also be communicatively coupled to each of the secondaryMAC modules 308B-N.

The hybrid primary/secondary MAC module 402 may receive data from theprocessor 202, select one or more of the secondary MAC modules 308B-N(and/or itself) and associated PHYs 210A-N for transmitting the data,packetize/process the data, and provide all or part of thepacketized/processed data to the selected secondary MAC modules 308B-N(and/or itself). The hybrid primary/secondary MAC module 402 may alsoreceive data from the secondary MAC modules 308B-N (and/or the PHY210A), combine/depacketize/process the data, and provide the processeddata to the processor 202. Thus, the hybrid primary/secondary MAC module402 may perform the functions of the primary MAC module 306 as well asthe functions of the secondary MAC module 308A.

In one or more implementations, each of the secondary MAC modules 308A-Nin FIG. 3 may be configurable to function as the hybridprimary/secondary MAC module 402. For example, the secondary MAC modules308A-N may elect one of the secondary MAC modules 308A-N to function asthe hybrid primary/secondary MAC module 402, the first of the secondaryMAC modules 308A-N in use may become the hybrid primary/secondary MACmodule 402, and/or one of the secondary MAC modules 308A-N may beselected at random to function as the hybrid primary/secondary MACmodule 402, such as for a predetermined amount of time.

In one or more implementations, one or more of the processor 202, theunified MAC module 204, the hybrid primary/secondary MAC module 402, thesecondary MAC modules 308B-N, the PHYs 210A-N, and/or one or moreportions thereof, may be implemented in software (e.g., subroutines andcode), hardware (e.g., an ASIC, an FPGA, a PLD, a controller, a statemachine, gated logic, discrete hardware components, or any othersuitable devices) and/or a combination of both.

FIG. 5 illustrates a flow diagram of an example process 500 of a primaryMAC module 306 in a unified MAC for multiple PHYs in accordance with oneor more implementations. For explanatory purposes, the process 500 isprimarily described herein with reference to the primary MAC module 306of the electronic device 102A of FIG. 3. However, the process 500 is notlimited to the primary MAC module 306 of the electronic device 102A ofFIG. 3, and one or more blocks (or operations) of the process 500 may beperformed by one or more other components or chips of the electronicdevice 102A, and/or by the hybrid primary/secondary MAC module 402 ofFIG. 4. The electronic device 102A also is presented as an exemplarydevice and the operations described herein may be performed by anysuitable device, such as one or more of the electronic devices 102B-C.Further for explanatory purposes, the blocks of the process 500 aredescribed herein as occurring in serial, or linearly. However, multipleblocks of the process 500 may occur in parallel. In addition, the blocksof the process 500 need not be performed in the order shown and/or oneor more blocks of the process 500 need not be performed and/or can bereplaced by other operations.

The process 500 is initiated by the primary MAC module 306 coordinatingdiscovery, association, and/or authentication with one or moreelectronic devices 102B-C, such as the electronic device 102C, via oneor more of the secondary MAC modules 308A-N, such as to establishcommunication channels over the one or more PHYs 210A-N(502). Forexample, the primary MAC module 306 may coordinate security mechanisms,key exchanges, etc., with the electronic device 102C across multiple ofthe secondary MAC modules 308A-N and associated PHYs 210A-N. In thismanner, the same security mechanisms can be reused for communicationchannels established with the electronic device 102C across multiple ofthe PHYs 210A-N, such as a 2.4 GHz PHY, a 5 GHz PHY, a 60 GHz PHY, andthe like.

Once the channels are established across the secondary MAC modules308A-N and the associated PHYs 210A-N, the primary MAC module 306 mayreceive link or channel quality information from the secondary MACmodules 308A-N with respect to the corresponding channels over theassociated PHYs 210A-N(504). The channel quality information mayinclude, for example, channel status information, signal strengthinformation, and/or generally any information that may be indicative ofchannel quality.

The primary MAC module 306 receives data for transmission from theprocessor 202 (506). The data may be, for example, packets, chunks, araw or unformatted data stream, or generally any form of data. Theprimary MAC module 306 packetizes the data and inserts sequences numbersinto the packets (508). In this manner, the sequence numbers can becoordinated across all of the secondary MAC modules 308A-N by theprimary MAC module 306. The packets may be, or may include, protocoldata units (PDUs), such as MAC PDUs (MPDUs), aggregated MPDUs (A-MPDUs),and the like. The primary MAC module 306 selects first and secondsecondary MAC modules 308A-B for transmission of the data based at leastin part on the channel/link quality information received from thesecondary MAC modules 308A-N (510). For explanatory purposes, two of thesecondary MAC modules 308A-N are described as being selected fortransmission; however, any number of the secondary MAC modules 308A-Nmay be selected for transmission, such as three of the secondary MACmodules 308A-N, four of the secondary MAC modules 308A-N, or any numberof the secondary MAC modules 308A-N.

The selection of the appropriate secondary MAC modules 308A-B fortransmitting the data may be based on one or more factors, such as, forexample, the link budget (assessed service availability) of each of thechannels, wireless link quality of the channels, the amount of data tobe transmitted, the power impact of the transmissions over therespective PHYs 210A-N, the availability of the channels over therespective PHYs 210A-N (e.g., as indicated by the associated secondaryMAC modules 308A-N), an amount of transmission delay that can betolerated by the data transmission, the bandwidth/throughput of thechannels, and/or a quality of service associated with the datatransmission.

In one or more implementations, the primary MAC module 306 may furtherdetermine whether retransmissions and/or acknowledgements should behandled by the primary MAC module 306 or the first and second secondaryMAC modules 308A-B, for example, based at least in part on a quality ofservice associated with the data being transmitted and/or an amount oftolerable delay associated with the data being transmitted. For example,if the data transmission is associated with a high quality of service ora low amount of tolerable delay, the primary MAC module 306 maydetermine that the retransmissions should be handled by the secondaryMAC modules 308A-N and that the acknowledgments should be transmitted bycorresponding secondary MAC modules at the receiving device. In thismanner, the acknowledgments and/or retransmissions can be handled withminimal delay.

However, if the quality of service associated with the data transmissionis lower, and/or the amount of tolerable delay associated with the datatransmission is higher, the primary MAC module 306 may determine thatthe acknowledgments and/or retransmissions should be handled by theprimary MAC module 306. In this manner, the retransmissions andacknowledgment packets can be aggregated at the primary MAC module 306for transmission over one or more of the secondary MAC modules 308A-Nand corresponding PHYs 210A-N.

The primary MAC module 306 determines an amount of a first portion ofthe packets to provide to the first secondary MAC module 308A, e.g.,based on the channel quality and/or throughput/bandwidth of thecorresponding channel and a total amount of packets to be transmitted,and the primary MAC module 306 provides the first portion of the packetsto the first secondary MAC module 308A (512). The primary MAC module 306may provide the packets to the first secondary MAC module 308A with anindication of whether retransmissions and/or acknowledgments for thepackets will be coordinated by the first secondary MAC module 308A orthe primary MAC module 306 (and/or the corresponding MAC modules at thereceiving device).

The primary MAC module 306 determines an amount of a first portion ofthe packets to provide to the second secondary MAC module 308B, e.g.,based on the channel quality and/or throughput/bandwidth of thecorresponding channel, and the primary MAC module 306 provides the firstportion of the packets to the second secondary MAC module 308B (514).The primary MAC module 306 may provide the packets to the secondsecondary MAC module 308B with an indication of whether retransmissionsand/or acknowledgments for the packets will be coordinated by the secondsecondary MAC module 308B or the primary MAC module 306 (and/or thecorresponding MAC modules at the receiving device).

The primary MAC module 306 receives packets from the first and secondsecondary MAC modules 308A-B (516). The packets may be, for example,data packets, acknowledgment packets, retransmission requests, and thelike. For example, when the retransmissions and/or acknowledgments arebeing handled by the primary MAC module 306, the secondary MAC modules308A-B forward the retransmission requests and acknowledgment packetsreceived over the corresponding PHYs 210A-B to the primary MAC module306.

The primary MAC module 306 combines the received packets (518). Forexample, the primary MAC module 306 may reorder the received packets andmay eliminate or drop any redundant packets. If the retransmissionrequests are being handled by the primary MAC module 306, and redundantdata was transmitted across multiple of the secondary MAC modules 308A-Band the corresponding PHYs 210A-B, the primary MAC module 306 maycompare the combined acknowledgments to the combined retransmissionrequests and may drop any packets requested for retransmission for whichan acknowledgment packet was also received. For example, if the samepacket was transmitted over two channels to another electronic device102C, and the packet was received over one channel but not the other,the primary MAC module 306 may receive a retransmission request for thechannel over which the packet was lost in addition to an acknowledgmentpacket for the channel over which the packet was received. Since theacknowledgment packet indicates that the packet was received by theelectronic device 102C over one of the channels, the primary MAC module306 can disregard or drop the retransmission request received over theother channel.

When the received packets are data packets, the primary MAC module 306may perform maximum ratio combining to combine the received packets anddrop the redundant packets. The primary MAC module 306 may provide thedata of the combined packets to the processor 202 (520). In one or moreimplementations, the primary MAC module 306 may depacketize the combinedpackets and may provide the depacketized data to the processor 202.

FIG. 6 illustrates a flow diagram of an example process 600 of asecondary MAC module 308A in a unified MAC for multiple PHYs inaccordance with one or more implementations. For explanatory purposes,the process 600 is primarily described herein with reference to thesecondary MAC module 308A of the electronic device 102A of FIG. 3.However, the process 600 is not limited to the secondary MAC module 308Aof the electronic device 102A of FIG. 3, and one or more blocks (oroperations) of the process 600 may be performed by one or more othercomponents or chips of the electronic device 102A, by the othersecondary MAC modules 308B-N of FIG. 3, and/or by the hybridprimary/secondary MAC module 402 of FIG. 4. The electronic device 102Aalso is presented as an exemplary device and the operations describedherein may be performed by any suitable device, such as one or more ofthe electronic devices 102B-C. Further for explanatory purposes, theblocks of the process 600 are described herein as occurring in serial,or linearly. However, multiple blocks of the process 600 may occur inparallel. In addition, the blocks of the process 600 need not beperformed in the order shown and/or one or more blocks of the process600 need not be performed and/or can be replaced by other operations.

Once a communication channel is established over a corresponding PHY210A, such as with the electronic device 102C, the secondary MAC module308A performs link management procedures with respect to thecommunication channel over the PHY 210A (602). The secondary MAC module308A also determines and/or receives channel quality information withrespect to the channel over the PHY 210A. The channel qualityinformation may include, for example, a signal-to-noise ratio value, areceived signal strength indicator, or generally any information thatmay be indicative of channel quality.

The secondary MAC module 308A provides the channel quality informationto the primary MAC module 306 (604). The secondary MAC module 308A mayprovide the channel quality information to the primary MAC module 306 ona periodic or an aperiodic basis and/or the secondary MAC module 308Amay provide the channel quality information to the primary MAC module306 responsive to a request therefor, such as when the primary MACmodule 306 has received data from the processor 202 for transmission.

The secondary MAC module 308A receives packets from the primary MACmodule 306 for transmission over the PHY 210A (606). In one or moreimplementations, the primary MAC module 306 may further indicate whetherretransmission requests for the packets should be handled by the primaryMAC module 306 or the secondary MAC module 308A. For example, theprimary MAC module 306 may insert a value in a header of the packetsindicating whether the secondary MAC module 308A should handleretransmission requests and/or the primary MAC module 306 may provide anindication separate from the transmission of the packets. If the primaryMAC module 306 determines that the secondary MAC module 308A shouldhandle retransmission requests for the packets, the primary MAC module306 may also provide an indication in the packets, such as in the headerof the packets, that acknowledgments corresponding to the packets shouldbe transmitted by a secondary MAC module of the receiving electronicdevice 102C, such as to minimize the latency associated with theacknowledgments as well as the retransmissions.

The secondary MAC module 308A transmits the packets over thecommunication channel via the associated PHY 210A (608). The secondaryMAC module 308A may perform one or more channel access procedures on thecommunication channel prior to transmitting the packets. For example,the secondary MAC module 308A may transmit request to send (RTS) framesover the PHY 210A and may receive clear to send (CTS) frames over thePHY 210A prior to transmitting the packets over the communicationchannel via the PHY 210A. In one or more implementations, the RTS/CTSframes may indicate a particular channel, frequency, and/or PHY 210Aover which the data will be transmitted, and the RTS/CTS frames can betransmitted to the electronic device 102C over any of the secondary MACmodules 308A-N, e.g., not only the secondary MAC module 308A.

If a request for retransmission is received with respect to thetransmitted packets (610), the secondary MAC module 308A determineswhether the primary MAC module 306 indicated that retransmission shouldbe coordinated at the primary MAC module 306 for the packets (612). Ifthe primary MAC module 306 indicated that the retransmission requestsfor the packets should be coordinated by the primary MAC module 306(612), the secondary MAC module 308A forwards the retransmissionrequests to the primary MAC module 306 (614).

After receiving the retransmission requests, the primary MAC module 306may determine whether the data actually needs to be retransmitted, e.g.based on acknowledgments received over other PHYs 210B-N. If the primaryMAC module 306 determines that the data needs to be retransmitted, theprimary MAC module 306 determines which of the secondary MAC modules308A-N should coordinate retransmitting the data. If the primary MACmodule 306 determines that the secondary MAC module 308A shouldcoordinate retransmitting the data, the primary MAC module 306 transmitsa command (and/or the data for retransmission) to the secondary MACmodule 308A. The secondary MAC module 308A receives the command or datafor transmission (616) and retransmits the requested data to theelectronic device 102C over the communication channel via the PHY 210A(618).

Similarly, if the primary MAC module 306 did not indicate that theretransmission requests should be coordinated by the primary MAC module306 (612), the secondary MAC module 308A retransmits the requested datato the electronic device 102C over the communication channel via the PHY210A (618). If the secondary MAC module 308A receives packets from theelectronic device 102C over the communication channel via the PHY 210A(620), the secondary MAC module 308A forwards the packets to the primaryMAC module 306 (622). If the received packets include an indication,such as in a header, that acknowledgements should be transmitted by thesecondary MAC module 308A, then the secondary MAC module 308A maytransmit an acknowledgment of the received packets to the electronicdevice 102C over the communication channel via the PHY 210A.

FIG. 7 conceptually illustrates an electronic system 700 with which oneor more implementations of the subject technology may be implemented.The electronic system 700, for example, may be, or may be coupled to, agateway device, a set-top box, a desktop computer, a laptop computer, atablet computer, a server, a switch, a router, a base station, areceiver, a phone, or generally any electronic device that transmitswired or wireless signals. The electronic system 700 can be, and/or canbe a part of, one or more of the electronic devices 102A-C. Such anelectronic system includes various types of computer readable media andinterfaces for various other types of computer readable media. Theelectronic system 700 includes a bus 708, one or more processor(s) 712,a system memory 704 or buffer, a read-only memory (ROM) 710, a permanentstorage device 702, an input device interface 714, an output deviceinterface 706, and one or more network interface(s) 716, or subsets andvariations thereof.

The bus 708 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal devices of theelectronic system 700. In one or more implementations, the bus 708communicatively connects the one or more processor(s) 712 with the ROM710, the system memory 704, and the permanent storage device 702. Fromthese various memory units, the one or more processor(s) 712 retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The one or more processor(s) 712can be a single processor or a multi-core processor in differentimplementations.

The ROM 710 stores static data and instructions that are needed by theone or more processor(s) 712 and other modules of the electronic system700. The permanent storage device 702, on the other hand, may be aread-and-write memory device. The permanent storage device 702 may be anon-volatile memory unit that stores instructions and data even when theelectronic system 700 is off. In one or more implementations, amass-storage device (such as a magnetic or optical disk and itscorresponding disk drive) may be used as the permanent storage device702.

In one or more implementations, a removable storage device (such as afloppy disk, flash drive, and its corresponding disk drive) may be usedas the permanent storage device 702. Like the permanent storage device702, the system memory 704 may be a read-and-write memory device.However, unlike the permanent storage device 702, the system memory 704may be a volatile read-and-write memory, such as random access memory.The system memory 704 may store any of the instructions and data thatone or more processor(s) 712 may need at runtime. In one or moreimplementations, the processes of the subject disclosure are stored inthe system memory 704, the permanent storage device 702, and/or the ROM710. From these various memory units, the one or more processor(s) 712retrieve instructions to execute and data to process in order to executethe processes of one or more implementations.

The bus 708 also connects to the input and output device interfaces 714and 706. The input device interface 714 enables a user to communicateinformation and select commands to the electronic system 700. Inputdevices that may be used with the input device interface 714 mayinclude, for example, alphanumeric keyboards and pointing devices (alsocalled “cursor control devices”). The output device interface 706 mayenable, for example, the display of images generated by the electronicsystem 700. Output devices that may be used with the output deviceinterface 706 may include, for example, printers and display devices,such as a liquid crystal display (LCD), a light emitting diode (LED)display, an organic light emitting diode (OLED) display, a flexibledisplay, a flat panel display, a solid state display, a projector, orany other device for outputting information. One or more implementationsmay include devices that function as both input and output devices, suchas a touchscreen. In these implementations, feedback provided to theuser can be any form of sensory feedback, such as visual feedback,auditory feedback, or tactile feedback; and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

As shown in FIG. 7, the bus 708 also couples the electronic system 700to one or more networks (not shown) through one or more networkinterface(s) 716. One or more network interface(s) may include anEthernet interface, a WiFi interface, a cellular interface, a mmWaveinterface, a reduced gigabit media independent interface (RGMII), orgenerally any interface for connecting to a network. The one or morenetwork interfaces 716 may include, or may be coupled to, a physicallayer module. In this manner, the electronic system 700 can be a part ofone or more networks of computers (such as a local area network (“LAN”),a wide area network (“WAN”), or an Intranet, or a network of networks,such as the Internet. Any or all components of the electronic system 700can be used in conjunction with the subject disclosure.

Implementations within the scope of the present disclosure can bepartially or entirely realized using a tangible computer-readablestorage medium (or multiple tangible computer-readable storage media ofone or more types) encoding one or more instructions. The tangiblecomputer-readable storage medium also can be non-transitory in nature.

The computer-readable storage medium can be any storage medium that canbe read, written, or otherwise accessed by a general purpose or specialpurpose computing device, including any processing electronics and/orprocessing circuitry capable of executing instructions. For example,without limitation, the computer-readable medium can include anyvolatile semiconductor memory, such as RAM, DRAM, SRAM, T-RAM, Z-RAM,and TTRAM. The computer-readable medium also can include anynon-volatile semiconductor memory, such as ROM, PROM, EPROM, EEPROM,NVRAM, flash, nvSRAM, FeRAM, FeTRAM, MRAM, PRAM, CBRAM, SONOS, RRAM,NRAM, racetrack memory, FJG, and Millipede memory.

Further, the computer-readable storage medium can include anynon-semiconductor memory, such as optical disk storage, magnetic diskstorage, magnetic tape, other magnetic storage devices, or any othermedium capable of storing one or more instructions. In someimplementations, the tangible computer-readable storage medium can bedirectly coupled to a computing device, while in other implementations,the tangible computer-readable storage medium can be indirectly coupledto a computing device, e.g., via one or more wired connections, one ormore wireless connections, or any combination thereof.

Instructions can be directly executable or can be used to developexecutable instructions. For example, instructions can be realized asexecutable or non-executable machine code or as instructions in ahigh-level language that can be compiled to produce executable ornon-executable machine code. Further, instructions also can be realizedas or can include data. Computer-executable instructions also can beorganized in any format, including routines, subroutines, programs, datastructures, objects, modules, applications, applets, functions, etc. Asrecognized by those of skill in the art, details including, but notlimited to, the number, structure, sequence, and organization ofinstructions can vary significantly without varying the underlyinglogic, function, processing, and output.

While the above discussion primarily refers to microprocessor ormulti-core processors that execute software, one or more implementationsare performed by one or more integrated circuits, such as applicationspecific integrated circuits (ASICs) or field programmable gate arrays(FPGAs). In one or more implementations, such integrated circuitsexecute instructions that are stored on the circuit itself.

Those of skill in the art would appreciate that the various illustrativeblocks, modules, elements, components, methods, and algorithms describedherein may be implemented as electronic hardware, computer software, orcombinations of both. To illustrate this interchangeability of hardwareand software, various illustrative blocks, modules, elements,components, methods, and algorithms have been described above generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application. Various components and blocks maybe arranged differently (e.g., arranged in a different order, orpartitioned in a different way) all without departing from the scope ofthe subject technology.

It is understood that any specific order or hierarchy of blocks in theprocesses disclosed is an illustration of example approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of blocks in the processes may be rearranged, or that allillustrated blocks be performed. Any of the blocks may be performedsimultaneously. In one or more implementations, multitasking andparallel processing may be advantageous. Moreover, the separation ofvarious system components in the embodiments described above should notbe understood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

As used in this specification and any claims of this application, theterms “base station”, “receiver”, “computer”, “server”, “processor”, and“memory” all refer to electronic or other technological devices. Theseterms exclude people or groups of people. For the purposes of thespecification, the terms “display” or “displaying” means displaying onan electronic device.

As used herein, the phrase “at least one of” preceding a series ofitems, with the term “and” or “or” to separate any of the items,modifies the list as a whole, rather than each member of the list (i.e.,each item). The phrase “at least one of” does not require selection ofat least one of each item listed; rather, the phrase allows a meaningthat includes at least one of any one of the items, and/or at least oneof any combination of the items, and/or at least one of each of theitems. By way of example, the phrases “at least one of A, B, and C” or“at least one of A, B, or C” each refer to only A, only B, or only C;any combination of A, B, and C; and/or at least one of each of A, B, andC.

The predicate words “configured to”, “operable to”, and “programmed to”do not imply any particular tangible or intangible modification of asubject, but, rather, are intended to be used interchangeably. In one ormore implementations, a processor configured to monitor and control anoperation or a component may also mean the processor being programmed tomonitor and control the operation or the processor being operable tomonitor and control the operation. Likewise, a processor configured toexecute code can be construed as a processor programmed to execute codeor operable to execute code.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” or as an “example” is not necessarily to be construed aspreferred or advantageous over other embodiments. Furthermore, to theextent that the term “include,” “have,” or the like is used in thedescription or the claims, such term is intended to be inclusive in amanner similar to the term “comprise” as “comprise” is interpreted whenemployed as a transitional word in a claim.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. Pronouns in themasculine (e.g., his) include the feminine and neuter gender (e.g., herand its) and vice versa. Headings and subheadings, if any, are used forconvenience only and do not limit the subject disclosure.

What is claimed is:
 1. A device comprising: a media access control (MAC)module communicatively coupled to first and second physical layermodules, wherein the first physical layer module is configured tocommunicate with another device over a first physical wireless channel,the second physical layer module is configured to communicate with theanother device over a second physical wireless channel, and the MACmodule is configured to: receive one or more data items to betransmitted to the another device; select at least one of the first orsecond physical layer modules for transmission of the one or more dataitems to the another device based at least in part on a first wirelesslink quality of the first physical wireless channel and a secondwireless link quality of the second physical wireless channel; andprovide the one or more data items to the selected at least one of thefirst or second physical layer modules for transmission to the anotherdevice.
 2. The device of claim 1, wherein the MAC module is furtherconfigured to: provide the one or more data items to the first andsecond physical layer modules for concurrent transmission to the anotherdevice.
 3. The device of claim 1, wherein the MAC module is furtherconfigured to: provide the one or more data items to the selected atleast one of the first or second physical layer modules for transmissionto the another device and at least one other device over one or morechannels.
 4. The device of claim 1, wherein the MAC module is furtherconfigured to: receive one or more other data items for transmission tothe another device, the one or more other data items being part of adifferent data flow than the one or more data items; provide the one ormore data items to the first physical layer module for transmission tothe another device; and provide the one or more other data items to thesecond physical layer module for transmission to the another device. 5.The device of claim 1, wherein the MAC module is further configured to:provide a first portion of the one or more data items to the firstphysical layer module for transmission to the another device; andprovide a second portion of the one or more data items to the secondphysical layer module for transmission to the another device.
 6. Thedevice of claim 1, wherein the MAC module comprises: a first secondaryMAC module communicatively coupled to the first physical layer module,wherein the first secondary MAC module is configured to perform linkmaintenance for the first physical wireless channel over the firstphysical layer module; and a second secondary MAC module communicativelycoupled to the second physical layer module, wherein the secondsecondary MAC module is configured to perform link maintenance for thesecond physical wireless channel over the second physical layer module;and a primary MAC module communicatively coupled to each of the firstand second secondary MAC modules, wherein the primary MAC module isconfigured to: receive the one or more data items from a processor; andselect the first or second physical layer module for transmission of theone or more data items based at least in part on the first wireless linkquality of the first physical wireless channel and the second wirelesslink quality of the second physical wireless channel; and provide theone or more data items to the selected first or second physical layermodule for transmission to the another device.
 7. The device of claim 6,wherein the first secondary MAC module is further configured to:determine the first wireless link quality for the first physicalwireless channel; and provide a first indication of the first wirelesslink quality to the primary MAC module; and the second secondary MACmodule is further configured to: determine the second wireless linkquality for the second physical wireless channel; and provide a secondindication of the second wireless link quality to the primary MACmodule.
 8. The device of claim 6, wherein the primary MAC module isfurther configured to: provide, to the first secondary MAC module, afirst portion of the one or more data items for transmission to theanother device based at least in part on the first wireless link qualityfor the first physical wireless channel; and provide, to the secondsecondary MAC module, a second portion of the one or more data items fortransmission to the another device based at least in part on the secondwireless link quality for the second physical wireless channel.
 9. Thedevice of claim 8, wherein the primary MAC module is communicativelycoupled to a third physical layer module and the primary MAC module isfurther configured to: perform link management for a third physicalwireless channel over the third physical layer module; determine a thirdwireless link quality for the third physical wireless channel; andprovide a third portion of the one or more data items to the thirdphysical layer module for transmission to the another device over thethird physical wireless channel.
 10. The device of claim 8, wherein thefirst secondary MAC module is further configured to: receive the firstportion of the one or more data items from the primary MAC module;provide the first portion of the one or more data items to the firstphysical layer module for transmission over the first physical wirelesschannel; and the second secondary MAC module is further configured to:receive the second portion of the one or more data items from theprimary MAC module; and provide the second portion of the one or moredata items to the first physical layer module for transmission over thesecond physical wireless channel.
 11. The device of claim 8, wherein thefirst secondary MAC module is further configured to: receive a firstportion of one or more other data items over the first physical wirelesschannel from the another device via the first physical layer module; andprovide the first portion of the one or more other data items to theprimary MAC module; and the second secondary MAC module is furtherconfigured to: receive a second portion of the one or more other dataitems over the second physical wireless channel from the another devicevia the second physical layer module; and provide the second portion ofthe one or more other data items to the primary MAC module.
 12. Thedevice of claim 8, wherein the first secondary MAC module is furtherconfigured to perform a first channel access procedure for the firstphysical wireless channel via the first physical layer module and thesecond secondary MAC module is further configured to perform a secondchannel access procedure for the second physical wireless channel viathe second physical layer module.
 13. The device of claim 6, wherein thefirst and second secondary MAC modules share a common MAC address.
 14. Amethod comprising: receiving, by a media access control (MAC) module,one or more first data items for transmission to a device, wherein theMAC module is communicatively coupled to a first physical layer modulethat is configured to communicate with the device over a first wirelesschannel and the MAC module is communicatively coupled to a secondphysical layer module that is configured to communicate with the deviceover a second wireless channel; selecting at least one of the first orsecond physical layer modules for transmission of the one or more firstdata items to the device based at least in part on a first link qualityof the first wireless channel and a second link quality of the secondwireless channel; and providing the one or more first data items to theselected at least one of the first or second physical layer modules fortransmission to the device.
 15. The method of claim 14, whereinproviding the one or more first data items to the selected at least oneof the first or second physical layer modules for transmission to thedevice further comprises: providing a first portion of the one or morefirst data items to the first physical layer module for transmission tothe device; and providing a second portion of the one or more first dataitems to the second physical layer module for transmission to thedevice.
 16. The method of claim 15, wherein the first portion of the oneor more first data items is the same as the second portion of the one ormore first data items.
 17. The method of claim 14, further comprising:receiving, by the MAC module, one or more second data items from thefirst physical layer module, the one or more second data items havingbeen received over the first wireless channel via the first physicallayer module; receiving, by the MAC module, one or more third data itemsfrom the second physical layer module, the one or more third data itemshaving been received over the second wireless channel via the secondphysical layer module; combining, by the MAC module, the one or moresecond and third data items; and transmitting, by the MAC module, thecombined one or more second and third data items to a processor.
 18. Themethod of claim 17, wherein combining, by the MAC module, the seconddata items and the third data items further comprises: eliminating atleast one redundant data item from the one or more second and third dataitems.
 19. A system comprising: a processor; and media access control(MAC) circuitry communicatively coupled to the processor, the MACcircuitry comprising: a plurality of secondary MAC modules, each of theplurality of secondary MAC modules being communicatively coupled to anassociated physical layer device; a primary MAC module communicativelycoupled to each of the plurality of secondary MAC modules, the primaryMAC module configured to: receive first data items from the processor;determine whether retransmissions for the first data items will becoordinated by the primary MAC module based at least in part on aquality of service associated with the first data items; provide a firstportion of the first data items to a first secondary MAC module of theplurality of secondary MAC modules for transmission to another deviceover a first channel via an associated first physical layer device, andan indication of whether the retransmissions for the first data itemswill be coordinated by the primary MAC module; and provide a secondportion of the first data items to a second secondary MAC module of theplurality of secondary MAC modules for transmission to the anotherdevice over a second channel via an associated second physical layerdevice, and an indication of whether the retransmissions for the firstdata items will be coordinated by the primary MAC module.
 20. The systemof claim 19, wherein the primary MAC module is further configured to:when the primary MAC module determines that the retransmissions will becoordinated by the primary MAC module: receive a first retransmissionrequest from the first secondary MAC module; receive a secondretransmission request form the second secondary MAC module; andconsolidate the first and second retransmission requests.
 21. The systemof claim 20, wherein the first retransmission request is for a data itemand the second retransmission request is for the data item, and theprimary MAC module is further configured to: determine one of the firstor second secondary MAC modules to retransmit the data item based atleast in part on respective channel quality information associated withthe first and second channels, respectively; and provide the data itemto the determined one of the first or second secondary MAC modules forretransmission.